#relativity
City on the Edge of Forever opens with the Enterprise in orbit around something that’s setting off the fireworks in the navigation console in front of poor Sulu. Spock is unperturbed, though, because he’s chasing Science: specifically, something he calls “ripples in time.”
Now, obviously, we know these time ripples are caused by the Guardian of Forever. But it’s pretty cool that we’ve actually observed an effect like this recently from Earth: we call them ‘gravitational waves’.
Gravitational waves are a consequence of Einstein’s theory of General Relativity, which says that massive objects (by which I mean anything that has mass) distort the space around them. When dense objects like neutron stars or black holes orbit each other, these distortions radiate outwards as gravitational waves, which are essentially ripples in spacetime. Although Einstein suggested this around a hundred years ago, they were only detected for the first time by LIGO in September 2015.
When the gravitational field changes, so does the speed of time. So technically, your head - which is further from the Earth’s center of gravity - is aging faster than your feet (although the difference is tiny - something like a few billionths of a second over an average lifespan). Hence, those gravitational waves also contained “ripples in time,” albeit very, very tiny ones, because they came from far away.
So ripples in time are real! Does that mean the LIGO detection was not a pair of merging black holes as has been assumed, but actually the Guardian of Forever? I vote yes.
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Stephen Hawking’s Final Theory on Black Holes | Physics Girl
What does Stephen Hawking’s last paper on black holes with soft hair say about the black hole information paradox? Paper source: https://arxiv.org/abs/1810.01847
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How Far Back In Time Can We See With Our Naked Eye?
“The oldest naked-eye starlight arrives from V762 Cassiopeiae, 16,300 years old: when humans first entered North America. Numerous visible globular star clusters are farther, with Messier 3 the most distant. It’s 33,900 light-years away, corresponding to the final demise of Earth’s Neanderthals.”
Albert Einstein lecturing students on the theory of relativity at Lincoln University, a public historically black University near Oxford, Pennsylvania on 3rd May 1946.
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The book “100 authors against Einstein” was published in 1931 to disprove Einstein’s Relativity. When Albert Einstein was asked to comment on this denunciation of relativity by so many scientists, he told the press;
“Why a hundred? If I were wrong, one would have been enough”
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The Theory Of Relativity - Stars
I am pretty much obsessed with this track. That beat is just too unforgettable.
Stars is one of those boundary-pushing bands whose genre is undefinable. It is almost as though Stars is a genre of its own. One can definitely sense the 80s influence, which just makes this band all the more amazing!
Set your mind on wide
Fall apart before they catch you baby
And never be just what they want you to be
Now that you’ve grown so wise
Use that head and stop to think a little
Just ‘cause you’re crazy doesn’t mean that you’re free
Back in lame grade ten I was a total devastator, baby
Down in the schoolyard they all fell to their knees
But it can’t be '93, sadly, 'cause I wish it could forever
You call it luck; I call it tragedy
What would you say?
If I fell apart
Could you bring me back there?
What would you say?
If I fell apart
Could you bring me back?
We got a rock DJ
We got a total fuckin’ alcoholic
We got a thing they call a cyber girl
A warm ovation please
For the dude who sold us ecstasy
He’s building homes now in the new third world
The snow just keeps on fallin’ in Hawaii and all stations west
Find someone close and hold them like you care
This is a race to the end and I don’t intend to win it, baby
You go ahead I’m gonna meet you there
Win it
Win it
B-A-D, used to talk of relativity
That was way back when everyone was scared
Now that we’re deep inside behind the wires, there’s a place to hide
You can do things they would’ve never dared
What would you say?
If I fell apart, could you bring me back there?
What would you say?
If I fell apart, could you bring me back?
So don’t be scared
There will be things we have dared
Don’t be scared
There will be things we have dared
From Willy Chyr’s Manifold Garden, a game you navigate by changing the direction of gravity in an MC Escher-esque world.
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Charge, Parity and Time Reversal (CPT) Symmetry
From our everyday experience, it is easy to conclude that nature obeys the laws of physics with absolute consistency. However, several experiments have revealed certain cases where these laws are not the same for all particles and their antiparticles. The concept of a symmetry, in physics, means that the laws will be the same for certain types of matter. Essentially, there are three different kinds of known symmetries that exist in the universe: charge ©, parity (P), and time reversal (T). The violations of these symmetries can cause nature to behave differently. If C symmetry is violated, then the laws of physics are not the same for particles and their antiparticles. P symmetry violation implies that the laws of physics are different for particles and their mirror images (meaning the ones that spin in the opposite direction). The violation of symmetry T indicates that if you go back in time, the laws governing the particles change.
There were two American physicists by the names of Tsunng-Dao Lee and Chen Ning Yang suggested that the weak interaction violates P symmetry. This was proven by an experiment which was conducted with radioactive atoms of colbalt-60 that were lined up and introduced a magnetic field to insure that they are spinning in the same direction. In addition, it was also found that the weak force also does not obey symmetry C. Oddly enough, the weak force did appear to obey the combined CP symmetry. Therefore the laws of physics would be the same for a particle and it’s antiparticle with opposite spin.
Surprise, surprise! There was a slight error in the previous experiment that was just mentioned. A few years later, it was discovered that the weak force actually violates CP symmetry. Another experiment was conducted by two physicists named Cronin and Fitch. They studied the decay of neutral kaons, which are mesons that are composed of either one down quark (or antiquark) and a strange antiquark (or quark). These particles have two decay modes where one will decay much faster than the other, even though they all have identical masses. The particles with the longer lifetimes will decay into three pions (denoted with the symbol π0), however the kaon ‘species’ with the shorter lifetimes will only decay into two pions. They had a 57 foot beamline, where they only expected to see the particles with slower decay rate at the end of the beam tube. In astonishment, one out of every 500 decays where from the kaons species that had a shorter lifetime. The main conflict with seeing the short-lived mesons at the end of the beam tube is because they are traveling relavistic speeds and therefore ignoring the time dilatationthat they are supposed to undergo. Thus, the experiment has shown that the weak force causes a small CP violation that can be seen in kaon decay.
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if the mass cannot reach the speed of light.
Why is the energy of mass obtained by multiplying it by the speed of light squared?
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“half of her beauty is her brain”
This is how the space around you would bend if you travel at near-lightspeed
Studying black holes … with water
Let’s continue the fun with analogies! Below we expand on the use of a particular analogy from science which we briefly discussed in a recent article.
The image above depicts the supermassive black hole M87*, which sits at the centre of the M87 galaxy some 55 million light years away. It was compiled from radiofrequency signals collected across several telescopes over two years. It is the first of its kind.
In the image we are given direct evidence of Einstein’s theory of general relativity. The black hole is dark, as predicted, since radiation cannot escape black holes once it’s within their boundaries. Moreover, the accretion disk (bright) around the black hole, from which radiation is emitted, is of a lopsided-doughnut shape. This varied brightness results from intense gravitational warping. And, because of rotation, there’s a kind of relativistic Doppler effect going on: radiation is boosted in the direction of rotation towards Earth.
Now, here’s a funny thing of relevance to us: some scientists and philosophers claim we can study black holes by investigating … [drum roll] … plain old water. One argument goes like this.
Inanalogue experiments, involving surface-water waves, something about black holes is realisable in surface-water waves’ ‘white holes’. Therefore, black holes can be modelled by analogy because their models and the models of white holes are related by the assumptions they share.
The analogy is not defined by a material relation. Nonetheless, thermal aspects of Hawking radiation (named after Stephen Hawking), which is released at black-hole boundaries, can be simulated in water. The analogy owes itself to ‘syntactic isomorphism’ between models, whereby the relation is confirmed in a ‘Bayesian sense’.
‘Analogue simulation’ is still a powerful experimental tool which can be used in a similar sense to computer simulation. Isn’t this cool? Or are such analogies fraudulent in some way because they only offer crude and opaque approximations via models which are often proven incorrect?
(Picture credit: Event Horizon Telescope project.)
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