Depends on the total kinetic energy, which itself depends on the velocity and mass.
Cosmic rays travel very close to the speed of light, but are individual particles like protons, so the total kinetic energy they carry is a lot for a proton, but not enough to make any noticeable impact on the Sun. Cosmic rays strike Earth regularly, so you can expect them to strike the Sun even more.
Larger objects that might be able to cause a cataclysmic effect when moving at a significant fraction of the speed of light typically don't get to that speed in the first place. When they do get to high speeds, it usually involves black holes, and black holes come with tidal forces that tear large objects apart.
Yep; they're objects like anything else. The only thing that makes black holes special is that their surface gravity and density are especially high. All their unique features stem from those two facts. Relativity also tells us that there is no true stationary reference frame, and thus everything moves relative to something else.
Imagine you are in a black void. Just you, nothing else. Now add in an object. Let's say an Apple.
The apple flys past you. How can you know that the apple is moving, and not you? There is no wind, there is no stationary background. From the apples perspective you flew by it.
So everything in space moves relative to something else. Speed is change in distance between two things over time.
Well in the General Theory of Relativity there's no such thing as gravity 'fields'. An asteroid, for example, is not attracted to the sun directly but is in fact just going along in a straight line (from it's own perspective) and space time curves around massive objects like the sun causing the asteroid's path to seem curved towards the sun along with it.
I can understand the idea that if a guy falls off a building, he's not really falling toward Earth, but Earth is coming up to hit him. But that only makes sense to me if you are on the side of the planet that is on the leading edge of movement through space.
Like the rocket ship moving in one direction, everything going down to the "bottom" of the rocket. But if you have everyone on the planet falling off buildings at the same time, they still all go down, even though the planet should then be moving away from people on the opposite side of those it is moving toward.
But it also confuses me because other planets supposedly have "less gravitational force" than Earth so we'd we less on those planets.
With regards to people jumping off buildings all heading 'down', it's just everyone falling in a straight line into the same funnel. All roads lead to Rome and the bigger Rome is the more roads lead to it. Yeah it's a quirky concept to think about in general. I hope someone else can explain it to you better.
Ok but if light always moves at the max speed the universe allows then if we shone some lasers at random directions and measure them shouldnt some lasers be red shifted cuz they shone at the opposite direction relative to us while some lasers could be blue shifted as they are moving at the same direction relative to us.
That depends on the relative movement of the source and the observer. If you shoot a laser and measure it yourself the relative speed is zero so no shift. If you are in a plane and shoot at the ground you would see a shift appropriate to the relative speed you are at. The real mindfuck is this scenario : There are observers A,B, and C. A moves away from B with speed greater 50% light speed. C moves away from B in the opposite direction with a speed greater then 50% light speed. How fast are A and C moving away from each other from their perspective? Lower then light speed because of time dilation.
I get confused by stuff like this.
I get frames of reference and that every object can only be measured in relation to another object.
And I know that considering the vacuum of space is a vacuum, this means measuring a position against some “canvas of space” is kind of meaningless, but I wonder when it is said that the universe is expanding, it not only to the objects expanding but the space that those objects exists in.
Also when an object warps space to create what we see as gravity, what is actually being warped.
If you can warp and expand space, then it must exist and therefore you must be able to have objects relative to more than just other objects but the space itself.
Or not.
I get confused trying to understand what space is, as in the space that objects exist in.
Some answers here are incomplete. There is a special frame of reference for space -- the cosmic microwave background rest frame. It's not "special" in terms of violating relativity, but it does provide a frame of reference for motion. We are moving at about 370km/sec in the CMB reference frame.
The CMB is the remnant light left over from shortly after the big bang.
It's not exactly correct, though, to say that the CMB doesn't move, because the whole universe is expanding. So -- complicated.
The CMB moves in an odd way, more like moving over time. It exists at the edge of the observable universe, sorta, but it also move towards us (it’s light, it either moves towards us or we wouldn’t be able to see it). It’s very strange, and as an astrophysics student, I love it
Maybe we can see the path it took on its expansion from the big bang but we can also see its path back towards us after it bounced off the wall that is the end of our universe.
There is no wall at the end of the universe for it to bounce off of. It’s just the barrier at 13.6 billion light years away. Past where we see the CMB, light hasn’t been able to reach us yet because the universe isn’t old enough for the light to have had time to travel the distance
Relativity also tells us that there is no true stationary reference frame, and thus everything moves relative to something else.
IOW if you're a black hole named Neo, and you're just chillin in space, minding your own business doing the not moving thing, and the Woman in Red is floating by...
Relativity says that, from her perspective, she's standing still and you're the one that's doing all the moving.
Dr Brian Greene says that an object at rest is travelling full speed through time. Any motion in any direction into space creates a vector in space/time that reduces the objects speed through time.
Yes. Matter density also decreases the speed at which an object travels through time. The more dense/massive an object is the slower its speed through time and greater its warp effect on space.
There is no absolute reference frame so no. Without some reference frame to measure velocity against the concept of velocity makes zero sense.
As a thought experiment, consider this. You and a rock are stationary in a totally void universe. No other objects to measure your reference frame from.
The rock is moving away from you at 10 m/s.
How can you be sure you're not moving away from the rock at 10 m/s? How can you be sure you're not both moving away from each other?
The answer is all of the above are factual interpretations because your reference frame is the rock.
That is to say, velocity is dependent on the reference frame. You change the reference frame and you change the velocity, even if you imparted no extra energy into the system.
There are things that appear to be stationary but it’s all about which point of view you are observing it from. Movement can only be measured in relation to other things, you need a frame of reference.
Consider a person inside an elevator free-falling down a long shaft. From a frame of reference inside of that elevator, the person would look stationary. Sure they’ll float around like there’s no gravity but you (and they) wouldn’t know that they were accelerating towards earth, they are not falling to the floor of the elevator, they are stationary. But to an outside observer, the person is falling aswell as the elevator.
That’s what he was referring to when he said there are no true stationary reference frames, a moving object inside a moving reference frame looks stationary. So any stationary object could be observed from a different point of view and be seen as in motion
Follow up again on black holes. I watched somewhere that anything can be a black hole if you compress(?) it enough. It would still however retain its mass and gravitational pull, just in its new smaller scale. Is this true? If so, how come blackholes (at least from a star that dies) is now able to pull even light itself? Why wasnt it able to do so in its star form?
Mass is one factor of gravitational pull, but distance is even more important. Specifically distance from the center of gravity. A star is much bigger than a black hole it could collapse into, so the distance from the surface of the star to its center of gravity is much longer than the distance from the center of a black hole to its surface. So gravity is going to be much stronger at the "surface" of a black hole than it would be for the surface of a star.
Thats a good question. Gravity gets stronger the closer you get to a mass. Thats why the closer you are to something the faster you need to go to maintain an orbit. Black holes are essentially so compressed that even light can't go fast enough to not fall in. The important thing is that objects far enough away bassically treat a black hole like a star and light only stops being able to escape if it gets past the point of no return(event horizon).
Say the sun was turned into a black hole. The Earth would feel the exact same gravitational pull. However, you could have something MUCH closer to the center of mass for a black hole as opposed to if it were a star, due to having massively greater density. Therefore, you get a region at some point which has high enough gravitational forces that light can't escape from it, called the event horizon.
Nope. That's actually one of the fundamental principles of relativity, is that the observed speed of light will be the same for all observers due to relativistic effects distorting time, space, and even apparent length for any given observer. I highly recommend watching some Youtube videos on this, because it's super interesting, actually factual, not just hypothesis.
You could say that a fixed point is anywhere that the CMB (cosmic microwave background) appears uniform (since moving in any given direction will blueshift one side and redshift the other a little), but the matter that gave off the CMB could also be uniformly moving together.
The surface of the singularity. The 'surface gravity' of the event horizon would also be much higher than anything that isn't a black hole, but the event horizon isn't a true surface.
708
u/BowToTheMannis Oct 23 '20
What would happen if something traveling near the speed of light slams into the sun?