Physics A-Level - Physblog

Showering with Meteors

8/20/2018

Last week I climbed atop a hill in a secluded country park and gazed skyward. The seemingly ever-static black canvas was anything but. To the untrained eye mere dots of white peppered the sky and that's that; a friend pointed out a plane (well done). To those with an astronomical bent: bright red Mars, Venus and Jupiter all came to say hello. Binoculars and telescopes pulled galaxies, stellar clusters, nebulae and an assortment of stars ever closer.

The prized guest, however, lay in the dead trails of an ancient icy beast. The Swift-Tuttle comet was 'discovered' in 1862 but possible reports of this comet come as early as 69 BC. With an orbital period of ~133 years this 26km diameter comet sheds it's icy shell when in close proximity to the sun; warming, melting and flaking. Comets' origins are not fully known although using the velocity, mass and trajectory of many known comets it has been shown that they emanate from two icy regions outside of our solar system known as the Kuipier belt (for short period comets) and the Oort cloud (long period comets). Projects are still underway to determine the nature of those regions, their structure and how they got there in the first place. (As a point of reference, Pluto (~1,200km diameter) was reclassified as a dwarf planet, and is the largest member of the Kuipier belt family).

And so, every 133 years Swift-Tuttle leaves a trail of dust and ice in it's wake and summarily returns to it's lair in the deep (probably the Kuipier belt), gathering strength (basically ice and dust again...) and will visit us again in the year 2126.

As chance would dictate, our precious Earth, every year, passes through that trail of ice and dust. The Earth is already travelling at 30km/s around the Sun! So when comet debris enters the Earths atmosphere it heats up and we observe that as a bright arrow across the sky.

It's really quite beautiful. And rather personal. The light from a meteor is only momentary, normally less than one second. You cannot predict where exactly it will emanate from, and, if in a small crowd, you could be the only person who sees it, to the annoyance of everyone else! After about 1hour and ~30 meteors later (...and a nice hot cup of tea), we headed home to sleep.

------------

The image is accredited to Fritz Helmut Hemmerich and featured on Astronomy Picture of the Day 12.08.18. It shows an unbelievable long exposure shot of the Andromeda galaxy (our closest spiral galaxy) and captures a Perseids meteor shooting directly across it, marvelous.

The Sun is HOT and we're going there!!!

8/16/2018

NASA this week launched the first ever human probe (Parker Solar Probe) who's final destination is our beautiful star "The Sun". It will reach speeds of 430,000mph, faster than any human object in history. It will do this with a gravitational assist, as it fly's past Venus on its way to the Sun and is 'sling-shot' using Venus's gravity to accelerate it. At it's closest, the Parker Solar Probe will reach a distance of 3.8 million miles from the Sun which is less than 5% of the distance of the Earth to the Sun.

The mission? To study the Sun's complicated dynamic interior and to better understand how these processes affect the Sun's ejected material (an important concern for Earthlings). The Sun's 'corona' is a glow of plasma surrounding the sun extending hundreds of thousands of miles outwards (see image); it can also reach millions of degrees (even hotter than the surface of the Sun!).

Solar flares spew out huge amounts of materials that can be many thousands of times greater in size than our own Earth. The frequency of solar flares vary along a 11 year cycle, peaking somewhere in the middle. Scientists know that the frequency of solar flares is related to the changing magnetic fields within the Sun. Dark 'sunspots' form as a direct result of these fields and typically last from a few days to months; they also accompany certain types of solar flares.

So many questions to answer... This NASA probe should shed light (or be shed light upon... or melted) on some of the unanswered questions relating to the dynamics of the Sun; our planet's most important source of energy. The energy arriving from the Sun in one hour is enough to power the whole economy for a year...! But lets not get carried away, that is a more completed fete than one would imagine.

By the way... its quite amazing that its taken so long to do this. We've directly photographed most planets up close (including that pesky 'non' planet Pluto), landed on comets and other planets' moons, landed on Mars and even sent probes outside of our solar system; yet this visit to our highly visible neighbour is quite unique.

To put this in perspective: In Carl Sagan's 1980 book "Cosmos", in the closing chapter he lists a whole bunch of future space projects that WILL HAPPEN. Looking at it now some say that he 'prophetically' lists all of those things that have indeed happened, and mostly in the order in which they did happen: landing on Titan, landing rovers on Mars, landing on comets, etc. Lets be realistic, space missions take years-to-decades to plan. Thinking of those future programs will take all the bright minds of now to make their wildest dreams come true in the future.

Its up to our highly skilled youth to make those dreams happen.

Image courtesy of wikipedia here.

Age Old Moon Crater Question... Resolved?

8/8/2018

The Moon's surface is better mapped than the bottom of our Earth's oceans. Although that may seem surprising, it makes sense. The Moon has no atmosphere, meaning that light dispersion doesn't blur or impede our view of it's surface. Even viewing the Moon through our own atmosphere at night can yield high resolution images.

In fact, you can use a x10 magnification binoculars and a smart phone (resting the two with a very steady hand!) and take a surprisingly good photo. With enough stacked images and some image processing a high resolution photo of the Moon can be captured with relative easy... our side of the Moon, that is.

So (!), despite the Moon's surface being well accounted for, the mechanism of formation of streak-like 'rays' emanating from craters was not fully understood. UNTIL NOW. This research article must surely give hope to any budding scientist who thought 'table-top' science was only a thing of the past. In the paper scientists drop marbles on to a bed of flour, mimicking the behaviour of an asteroid impacting the Moon. Awesome.

What they observed was that marbles falling on flour that had been flattened shows a uniform circular spread of 'dust' forming around the impact sight. HOWEVER, when the marble impacts an uneven bed of flour (e.g. a bumpy grid of hexagons), rays or streaks emanate away from the impact sight. They explain that a bumpy surface concentrates shock waves along specific paths that breaks the normal symmetry of impact on a flat surface. This channels the ejected material along specific paths.

What is fascinating is that they found that the relative size of the marble to the spacing of the bumps in the flour actually determines the number of rays that emanate from an impact site. This is very useful! It means that astronomers can look at the craters on the moon, count the impact rays and then estimate the topography of the moon and/or the size of the asteroid that must have hit it. Given that the Moon has hundreds of thousands of craters, with some big-data analysis, scientists will be able to find out the size distribution of asteroid impacts for the past (however many) millions of years!

For some perspective... Check out this video that shows how some research initiatives constantly monitor the Moon for new impact sites. This can number hundreds of new craters every year.

Water Discovered!... on Earth?!

8/5/2018

The story of the origin of water on Earth is unresolved.

An interesting twist is that we now know that there is water trapped deep under the Earth's crust in the mantle and 'transition zone' (~500km under the surface) mainly in the form of crystals called ringwoodites (see image opposite, courtesy of University of Alberta) and wadsleytes. They are, of course, rather hot, and water doesn't exist in liquid form 500km under the surface.

However, when these crystals are spewed out to the surface of the earth from volcanoes, scientists can measure their composition using x-ray spectrometry. These crystals contain hydroxide ions (hydrogen and oxygen bound together), or crystal defects that have the potential to liberate a huge amount of water under the right conditions, such as reactions with hydrogen or melting.

How did it get there? Where did it come from? Is Earth unique? What can geophysical measuring techniques teach us about the finer structure of the Earth's interior? Can this water be mined and its contents released, or harvested? Will spaghetti really always break in to three pieces?... Ok that last question was not relevant.

The estimated water content in the 'transition zone' is up to a few times the water content of the oceans... thats a rather large amount!

Two prevalent theories of how water got embedded so deep is: 1) Water that was around during the formation of Earth clung on to dust and coalesced, and made its way in to a self-ordered layered formation (much like liquids of different densities separating), 2) layer formation from regular asteroid impacts containing water...

This doesn't tell us much though. Because if I were to ask you 'how did it get there', you could probably come up with those two options. The difficulty is measuring in situ (i.e. in an actual place where the things happen) and making physical models to describe a whole host of complex interactions including heat gradients, different materials, liquid motion of mantle, dynamic crystallization on large scale, time, gravity, seismic activity, etc. That is no simple matter.

At present, experiments using seismic waves are underway to get a higher resolution picture of what is going on beneath the surface and analyses of crystals spewed out from the 'underworld' also provides insights into the origins of water deep inside the Earth.

Either way, it is fascinating that water, or at least the materials for its liquid form, exists in what was thought to be a most unlikely place.

https://www.quantamagazine.org/the-hunt-for-earths-deep-hi…/

Finally, a Swimming Pool on Mars

7/25/2018

Well... before we get excited, what is really there? Where is this water? How big is it? What is its composition? What does this say for life of Mars?

Scientists estimate that the body of water is a minimum of 1m deep and likely to be trapped under ice. Interestingly, it is deduced that the lake is composed of a high salt concentration, making it less likely that it will freeze. Highly concentrated brine lakes pose a decreasing likelihood of life "as we know it". That caveat is important, because, in truth, we don't know what life would look like outside of Earth, but its certainly promising news. It seems like liquid water was once present on the surface of Mars, but that is long gone...

Life, on Earth, has been found in extreme heat and chemical conditions (like around deep sea volcanic vents), where water plays a central role in bio-chemical processes important for life. "Extremophile" bacteria have now been found in highly acidic, alkali, hot, cold and more. Another example of wiidely distributed life is tardigrades (although admittedly much bigger and more complicated than simple single cell organisms!) and have been shown to survive cryogenic freezing for decades and even the vacuum of space! Theres no telling what or how life can vary since.... we just don't know what it could look like.

Satellite imaging techniques like these need to be refined and could help find more such bodies of water. Methane lakes, for example, have also been found on Titan, Saturn's largest moon.

Can we go to this lake?! It may be too far under ice for current robot technology and space delivery systems to tackle, although it seems like a real option for future Mars missions since water is the 'holy grail' of the signature of life 'as we know it'.
Do you think there is life outside of Earth? Answer in the comments!

https://www.bbc.com/news/science-environment-44952710
https://en.wikipedia.org/wiki/Lakes_of_Titan

Ants Will Steal Your Cheerios... sort of

7/19/2018

Fascinating research from the Weizmann Institute is aiming to understand the cooperative behaviour of ants to deliver food to their nests.

Ants are well known for being able to carry/move much more than their body weight, but how do they know which way they're going? Who's role it is to do what? How do they correct their path? How is all of this information communicated? Can this be modeled somehow for human purposes such as creating a robot ant army or a flying drone army to autonomously deliver packages or rescue people from a wreckage...?

The research describes how some ants act as 'lifters' and some as 'pullers' to physically move a piece of food (a cheerio!). 'Pullers' align their body parallel to the direction of motion to maximise the force exerted on the cheerio whereas 'lifters' simply lift the cheerio to reduce friction with the surface. As the cheerio moves, each individual ant corrects their body alignment and exerted force.

There are lead ants which regularly prod the collective group in the direction of the nest. They also describe how the roles of different ants can change during carrying, and how that is communicated to the group. There is essentially an 'unspoken' feedback mechanism whereby all corrections are made individually, but externally guided by the leader ants. The feedback sensitivity is such that the cheerios don't spin out of control, or that the cheerio doesn't overshoot its intended destination.

The research paper demonstrates the utility of using statistical physics to explain the motion of multi-component forcing to quite beautifully describe the collective motion of ants...!

https://www.nature.com/articles/s41567-018-0107-y

And Man Said: "Let us make Brains"

7/12/2018

And man said: "Let us make Brains", and they did.

Sergiu Pasca from Stanford University has been working on growing brains from stem cells. Stem cells are the initial cells found in growing embyo's that differentiate to form the structures of every organism. A cell can be differentiated (i.e. initiated for a certain task) using chemical techniques and has now been utilised by Pasca and his colleagues to create a remarkably "realistic" rudimentary brain... a few millimeters in length.

Although, this is a far cry from making bio-cyborg engineered humanoids, the research is promising in that it provides a platform to study and model human brain tissue that is normally hard to come by, for obvious reasons! This has obvious ramification for the development of our understanding of neuro-degenerative diseases and brain disorders.

It will take a while to arrive at a something remotely resembling 'normal' brain function. But the research is a starting point, yet opens a whole Pandora's box of ethical issues that scientists have been grappling with for a while, in the hope that once these experiments become a reality we will be better prepared to deal with the ethics.

https://www.pascalab.org/
https://www.nature.com/articles/nmeth.3415
https://www.nature.com/articles/s41567-018-0200-2

(Brain image is from the article in the second link, Also found in a google image search!)

First Protoplanet Imaged!

7/4/2018

Stunning first images of first protoplanetary disk WITH PLANET!

For decades the mechanism by which planets form around stars was not fully known. In the early stages of planet formation, gas surrounding a central star (typically in a nebula) spirals around that star forming a disk called an 'accretion disk'. Within this accretion disk it is believe that gas (and/or clumps of matter) accumulates to form planets. This accumulation of gas in to a planet would be seen as a gap (or dark ring) at the radius at which that planet is formed.

This is exactly what was reported by scientists working with data from ESO's aptly named "Very Large Telescope" (VLT).... not to be confused with the "Extremely Large Telescope"!

Interestingly enough, this planet is at a distance from its star similar to that of our Sun and Uranus, but its temperature is 1000degrees Celcius (Uranus is ~-215degrees). The scientists were also able to observe features of the atmosphere and composition of the gas giant, named PDS 70b.

Great news for the astrophysics community.

However, one image cannot explain the full picture and the many other possible mechanisms of planet formation. We will need to wait and see until the data is in... lots and lots of data.

https://www.sciencedaily.com/releas…/2018/…/180702094040.htm

The Mystery Image... oooooooooo

6/25/2018

Check out this photo, from my masters degree, way back when...

Can you guess what it is? Scale? What type of image?

Stealth material hides objects from infrared eyes

6/24/2018

Whats interesting here is that this material is not new... this research group make a mat of needles that adsorb a shed load of light; so much so that one could avoid detection. However, they make those needles slightly longer than had been previously achieved, and show that it not only absorbs visible light, but also infrared.

This has an obvious 'cool' factor, and the applications of such a material is quickly seen by those striking images in the article.

How innovative is this material? Somewhat. Has it changed the arena of science? Probably not. Are its potential applications interesting? Hell yeh! And thats good enough for me.

https://www.sciencedaily.com/releas…/2018/…/180622174752.htm