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In Laser Thruster Advance, Light Alone Pushes a Sled Down a Track

Here is the latest demonstration of a propulsion technology called a photonic laser thruster. In it, NASA Innovative Advanced Concepts Fellow Young Bae moved a one-pound object on a track using light alone for the first time. 

The hope is that a laser fired from one spacecraft to another will provide enough push to make this form of propulsion viable for interplanetary travel. Back in 2013, the agency expanded research on the concept of photonic laser thrusters after discovering it could have “a much larger potential in NASA mission applications.” 

Czytaj dalej

Please help us pass physics and signal boost.
So my physics teacher is a huge Anna Kendrick fan and he said if she followed him on Twitter we would all get full credit on our final exam. He said if we got 1,000 retweets the same rules apply. Help us beat the public school system.

The Seeds of Unified Physics go back a long way in the history of scientific theory. In some of the earliest historical records of human culture we find civilizations around the world that believed in the Presence of a Unifying Field of Energy that surrounds and permeates all things. This Dynamic Energy Field provided an underlying organizing framework and was considered by some to be the Source of Life Energy within biological systems, being given such names as Chi (China/Asia), Ki (Japan), and Prana (India). In the early pursuits of Science and Physics (going as far back as Plato) it was often referred to as the Aether and was proposed to be the Medium through which Light travelled. Though it was eliminated from the general scientific paradigm in the early 20th century, the indications for an Underlying Field persists as being inherent in the Fundamentals of Physics.

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Habitable Exoplanets Debunked! By PBS Spacetime

Kepler 186f rekindled our hopes and dreams of colonizing space. “Habitable exoplanet!” we heard, “Space Travel IS NOW!” Top that off with multiple breakthroughs in companies like SpaceX and BAM. The Future is now! But there’s a small problem… When we say a planet is habitable, we aren’t REALLY saying what we think we are saying. “Habitable” means something else. Is Kepler 186f habitable, in the true sense of the word? And if not, what other planets should we be looking at? Watch this episode of PBS SpaceTime and find out!

sphere-sounds zapytał(a)::

I think I can officially blame you for being the behind my getting into SU, which is a cute, hilarious and increasingly interesting show (esp. after the episode I watched last night, "Ocean Gem"). As you probably remember, in said episode Lapis Lazuli uses her powers to drain the world's oceans to construct a tower in a desperate bid to get home. Now given what we know about the volume of the seas and the apparent diam. of the tower onscreen (against her & Steven) - can we say how tall it was?

Ahahaha, another convert :D

That’s not too hard really. Though of course we need to note that (the animators have explicitly said) Steven Universe is not drawn to scale! Different characters are different heights compared to each other in different shots. So we can’t say that Steven or Lapis have a canonical height based on some other comparison!

Nevertheless, we can make approximations and assumptions. So.

At the bottom, Lapis’s water column appears to just be a big cylinder.

Steven is being lifted up in the middle.

Towards the top, the column has split into a number of smaller cylinders which terminate at different heights.

Steven and Lapis meet on the highest subcolumn.

The apparent thickness of this column varies from shot to shot. In this shot, it looks like it’s a few Lapis-lengths wide, but in closer shots, it seems much bigger.

Which is of course because, like I said, it’s not supposed to be a scale drawing :p

Nevertheless, we can make some estimates. To me it looks like the platform is at most a few tens of metres wide. The main column consists of many such columns, so it’s likely at most a few hundred metres wide. Let’s just call it 100m for approximation’s sake. So the area of the platform is \(\pi r^2\approx 8000\unit{m^2})

According to Wolfram Alpha, the total volume of water in Earth’s oceans, seas and bays is \(1.332\times10^9\unit{km^3}\) (not that this many sig figs matter which such a rough estimate of the size of the platform!). Dividing this volume by the estimated area puts the height of the column at about 1000 astronomical units, i.e. 1000 times the distance from the Earth to the Sun.

This is clearly not what we see in the pictures! Lapis appears to be roughly at the height of low Earth orbit - I’m saying that because the curvature of the Earth’s horizon that we see in the picture seems pretty similar to photos from the International Space Station, which is in a low Earth orbit. If Lapis was 1000au away from Earth, the Earth would be a distant, barely visible speck. That said, Lapis is not in low Earth orbit, because she is still travelling with the surface of the Earth - to attain orbit she’d have to move a lot faster.

Even if the platform is about 10 times wider than my estimate (a kilometre across), that would still be 10au. So it seems Lapis is not using the entire volume of the oceans to build her tower.

One further observation: even if she’s “only” climbing to the height of low Earth orbit, if Lapis’s tower is in hydrostatic equilibrium, the pressure at the bottom would be ridiculous. The Earth’s deepest oceanic trench is \(11\unit{km}\) deep, and a low Earth orbit is defined as being between \(160\unit{km}\) and \(2000\unit{km}\), so the pressure at the bottom of the tower would be (as to a first approximation it scales linearly with depth) around sixteen times the pressure at the bottom of the Marianas trench at mimimum, probably more.

So Lapis must be suspending all the water she is using against gravity, not just confining it to the tower. This is also consistent with the fact the the weight of the tower isn’t piercing a deep hole into the ocean floor.

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No, Your Microwave Isn’t Dangerous - Food Myths #1

The first one is one we’ve heard a lot: microwaving your food zaps the nutritional value. Watch to find out why that’s a lot of malarkey.

By: ACS Reactions.

I saw this comic once about “purity”. And I’ve realized that my interests have become increasingly “pure”. When I was younger, maybe elementary and middle school, I was very interested in the social sciences. In high school I loved biology. My sophomore year of college I moved on from a biochemistry major to a chemistry major. And here, the summer between junior and senior year, I am a chemistry and physics double major who mainly prefers physics.

So… In two months am I going to be a mathematician? What comes after math? What is the limit as purity approaches infinity? Is it philosophy?

Theoretical physics is essentially mathy philosophy, so my interpretation of this data is that I’m destined to be a physicist.

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Pythagoras Cup (Greedy Cup) filled with Mercury

This features features Professor Sir Martyn Poliakoff from the University of Nottingham.

Numberphile for Pythagorean math: https://youtu.be/ItiFO5y36kw
Buy a Pythagorean Cup on Amazon: http://bit.ly/Pyth_Cup

By: Periodic Videos.

My PI sent me an email a couple hours ago saying we’re going to have a research group meeting tomorrow at noon and that we need to be prepared to share a detailed plan for the entire summer and our goals, specifically that we need to list subtasks that lead up to our goals.

I. Don’t. Know. Because I’m meeting with the organic chemist tomorrow at 12:30 to talk about what I’ll be doing. Sigh. Thankfully I have a paper where my PI wrote down pretty much what he wants me to do, so I’ll go off that.

He also wanted a detailed task list for the following week. That one’s easy. Drown myself in literature so I am prepared to order my chemicals on Monday, when our spending freeze is… defrosted. Then for probably two weeks after that drown myself in more literature because I have to wait for my chemicals to come in… Meaning I pretty much have nothing to do until mid-June. Maybe I can help Spencer, the guy working on the old lithium chloride emulsions, with something in the mean time so I’m not just sitting on my ass for three weeks. I want to show that I care and am eager to do the things.

As a side note, my PI calls our research group the “FaNS” (Fast Neutron Spectrometry). I thought that was whimsical somehow.

She could walk through a garden of wilting flowers and breathe life into them all. The sun couldn’t provide for them, but she revived them. Because she had galaxies of light within her, she could be their sun. She is my sun.
She is always shining.
Today in physics I learned about how certain things behave with light. Some things like diamonds have so much light within them, and rays that can barely escape into the air. Instead, all the light they emit is reflected back into them, and that’s why they sparkle. With all of the light in her, all the power to revive flowers and lives of those who are living in darkness, with her being as radiant as the sun, I suppose that’s why she shines.
—  Pent-up-venting