8 Minutes

If I understand that right, gravity also moves in space at the speed of light, therefore Earth will keep on orbiting for 8min around nothing?
- Kind of. The concept of simultaneity breaks down at distances where the speed of light matters. If we base it on what we currently observe and call "now" on the Sun the eight minute old state we currently observe then what does "now" on earth look like from the point of view of the Sun at that same moment? You can't reconcile a single "now" for observers in both locations.
  An alternative take which is also consistent with observable physics is that the speed of light is infinite but it's causality itself that propagates at c.
  Thinking in those terms also makes a number of relativistic effects more intuitive. You need infinite energy to reach the speed of light simply because it's infinitely fast. Time dilates when moving because you're encountering approaching causality earlier than you otherwise would have. Time "stops" for anything traveling at the speed of light because at infinite speed it just experiences literally everything in its line of travel at once and the concept of "after" becomes meaningless, encountering all future oncoming causality in a single instant.
  This was a bit of a tangent but it's something that has fascinated me for a long time.
  
  I'm trying to understand how that reference frame works when you just just bounce a photon off a mirror and time how long it takes to come back? Like, light must have a non-infinite speed to the stationary observer, or it wouldn't take time to traverse the distance.
  
  Information can only travel at the speed of light.
- It's sort of how if you hold a slinky on one end hanging down, then drop the slinky, bottom will not start falling until the top reaches it. In a sense, bottom will be hanging onto nothing. But of course that nothing is tension from the top of the slinky.
- That is correct as weird as it sounds
- The sun could be gone but its influence would remain. Kinda like getting out of a pool and looking back to see the waves on the surface that you caused.

Wouldn't you see the effect on the moon?
- Only if the moon is up.
  
  Moon is a fake bitch.
- Imagine seeing the moon just switch off
  
  That would be a beautiful, terrifying sight. You could gaze up at the most amazing view of the stars as the whole world froze to death.
  
  There is a really great short story by Larry Niven based on a similar premise:
  "Inconstant Moon"
  There is also an "Outer Limits" episode based on this. I watched that before knowing the short story and it is one of only 2 or three OL episodes that I still have an active memory of...
- Yup
- If you can see the moon (if it is "up" at night).
- There's a pretty cool short story where a guy is looking at the full moon and he realizes that it's gotten way too bright, and that could only happen because the sun has just spontaneously exploded, and he basically just makes peace with the fact that the world is going to be destroyed very shortly.
- Assuming its midday, and the moon is on or near the horizon, it would actually still be seen for an additional 1.3 seconds after we see the sun disappear. If its high in the sky however, it would disappear only a few ms after the sun, unless it was in a full or partial eclipse, where it would disappear at the same time to our eyes.
- Yeah - half a second before seeing it on the sun.

It goes to 9 minutes from 8, since every single communication gadget will yell out that the sun has disappeared as reports come in from the other side of the earth.
- Depending on the lunar cycle, the night time side would notice the moon become dim.
  
  ~~dim~~
  Disappear
  
  Doubt anyone would notice the moon getting dim when the fucking sun disappears in the same second.

That is actually correct. The difference of being on the opposite side that faces the sun is just a few thousandths of a second, but it is there.

Now I am curious, somebody explain. if it just stopped burning, would we know after 8 mins, if we lived on the opposite side?
- Moon would "disappear" when it no longer reflected Sun's light.
  It would also start getting very cold fast
  
  It would probably take more than a day for the cold to be so intense that you can't possibly explain with some normal local phenomenon.
  
  The moon might be on the daylight side, so we wouldn't necessarily observe that.
  
  Any visible planet or asteroid would. So some stars would also appear to blink out, but those would take longer to blink out. So the moon would go after 8 minutes, Jupiter would take 43 minutes to stop receiving light, and another 35-52 minutes to disappear for earth depending on orbital locations.
  Presumably we would get something on radio/tv/internet from the side facing the sun once they realized it, that of course being only if they hadn't already been eradicated by a horrific shockwave caused by whatever event caused the sun to vanish before they had a chance to report what they saw, because supernovae tend to travel at very close to the speed of light, so there wouldn't be much time for them to react.
  And if this is a supernova, you might just have time to grok what happened before the planet was obliterated under your feet from the shockwave.
  So I guess... chances are we would just barely understand what happened before we were gone.
  
  Does heat travel at the speed of light? I just realized I have no idea how the heat from the sun travels to earth.
  
  I wonder how cold how fast.
- It takes 8 minutes for the light to travel from the sun to Earth. Because light in a vacuum travels faster than anything, including information, we would not and could not know it had disappeared for 8 minutes. This means Earth would continue to follow its orbit around a non-existent sun for 8 minutes because the Sun’s gravity would still be acting on the Earth.
  If it was nighttime, you wouldn’t notice the sudden lack of sunlight (other than if it was a full moon) but you’d almost certainly notice the change in gravity.
  Edit: actually, you wouldn’t feel any difference in gravity or experience any change of acceleration. What you would experience is a very tiny vibration, of 1 million push notifications being sent to your phone from the other side of the planet.
  
  I don't think you'd actually "notice" the gravity.
  Earth would still retain it's mass, and we're much closer to it, so it's lesser mass acts much more on us than the sun's greater.
  Though, the earth would stop orbiting the sun and ~~travel on a mostly tangential path~~ travel nearly radially away from where the sun was, instead of the elliptical path it currently travels.
  This is a very interesting physics question that I may look into further. Specifically what would the theoretical acceleration be, due to the lack of the sun? Is it above a humans level of perception?
  
  Interesting, so you are saying light is faster than gravity?
  
  you’d almost certainly notice the change in gravity.
  Really? can you actually percieve the sun gravity? Do you mean that we would get like a tsunami beause of the tidal effect? Now I kinda want a documentary about this.
  
  It's weird to say that light travels faster than information, because light is information. In other words, top speed for information IS speed of light.
- Yes, because of the medium of communication you are using right now.

I'm more interested in how long before we freeze to death.
How long will the earth's atmosphere hold onto its heat?
- The classic sci-fi short story A Pail of Air touches on this.
  https://www.gutenberg.org/ebooks/51461
- I'm more interested in how long before we freeze to death.
  Kurzegesagt did a great video on this thought experiment: https://www.youtube.com/watch?v=gLZJlf5rHVs&t=1

But we do have Twitter now.
- Not anymore…
  
  Or they will postulate its the left who put up a fake screen on the sky

The moon would disappear though, so you'd notice by looking at the sky if it wasn't obstructed by clouds.
- Only if the moon is on your side of the planet at the time and not already eclipsed by earth's shadow.
  We are however very connected. That shit would be global news immediately.

If the sun disappears when? According to GR's conception of simultaneous events, it disappears immediately.
- Which two event are you talking about being simultaneous? The Sun going out and Earthers observing it? Those things will not be simultaneous in any reference frame, because they are "light-like" separated. (ie they lie on a 45 degree line in a Minkowski plot.)
  
  I think what he means is when the light from the sun disappearing arrives at earth, that’s effectively when the event of the sun disappearing happened from the earth’s perspective.
  
  Yep. Imagine you’re off in space such that you, the sun, and the earth make an equilateral triangle. The sun disappears, then after 8 minutes you see it disappear. Then after ANOTHER 8 minutes you see the earth go dark, because that light had to cover two of the 8-light-minute long legs of the triangle.

Technically true since the daytime side will know first.

Well they're not entirely wrong... I mean I turn off my notifications when I go to sleep.

unless you're sleeping - 8 minutes and maybe 30 seconds to start seeing posts online, 10 minutes to start getting news about it
- I don't know about you, but if I start seeing headlines about the Sun vanishing, I'm assuming it's a hoax and going back to bed.
  
  Maybe if ony one or two places are reporting on it. If all the major 'reputable' news sources are reporting it; there's a pretty good chance there's something to it.

All we can see is 8 minutes into the sun's past.
- What if I have a flashlight and am underground?

In about 8 minutes and 20 seconds, we would lose the Sun’s gravitational force. Namely, gravitational waves travel at the speed of light (186,000 miles per second or 299,000 kilometers per second). This also means that we would be in complete darkness 8 minutes after the Sun disappears
https://curiousmatrix.com/what-would-happen-if-the-sun-disappeared/
- What I wanna know is if gravitational waves travel at the speed of light all the time or are they influenced by media like light.
  
  I’m 0% an expert in this, but I think they move at light speed all the time. Light is “affected” by mass only indirectly, since the light travels in a straight line through local space but space itself is curved by the mass.
  
  Light gets caught up in mediums because those mediums have electric fields (the electrons for matter, or light itself when interfering). Thus, gravity waves will be slowed by gravity fields, like planets, stars, and galaxies.
  What waves interact with also depends on the wavelength, like how radio waves can bounce off Earth's ionosphere, but can ignore the atoms in the walls of your house. There are plenty of very large gravity waves from merging black holes and neutron stars, and those pass right through Earth. Smaller gravity waves (like from a collapsing or disappearing star) could interact with other stars, possibly reflecting off of star clusters, or even refracting through like glass if the distances were regular and the waves just the right length.
  Those waves would also be delayed, just like light in glass, air, or water. Interestingly, even light still moves through these mediums at light-speed, but all it's energy moves slower. If you had a sensitive enough detector you could see heavily attenuated light that didn't slow down.