Had to read the article to find out that they mean 72 “years worth of orbits” happen in 1 earth day. Although unlikely I was hoping that it was orbiting so fast that 1 earth day there would pass 72 earth years to a stationary observer due to time dilation. Not sure how fast it would need to go for that to happen.
Since time and speed are relative, to have 1 Earth day on the star and see 72 years on Earth, it’d simply be a speed multiplier of 72*365.24= 26,296.28 times faster. Our solar system orbits the galactic center at 250km/s or 0.0008c, so ~26k times that puts it at nearly 22c relative to us. So no.
But quite frankly, there must be a way to be a slower observer. Earth’s orbital speed is about 30km/s (0.0001c) so that drops the product way down to 2.6c. And while the Parker Solar Probe holds the record for the fastest man made object at 0.0006c at its closest solar approach, it actually took a lot of energy to slow it down to get it to the sun and stall it’s orbit. Otherwise, it’d just orbit it the same as the Earth. It slides out to a Venusian distance from the sun at apogee and drops to 12km/s, halving the differential requirement to +1.2c. But if everything is relative, how do we even determine where 1c is and know it’s so definitively impossible to reach? I don’t know, I’m starting to have an existential crisis. Maybe time just keeps dilating and simple addition/subtraction doesn’t apply for appreciable values of c so you have to start multiplying in decimals.
Relativistic time dilation is nonlinear, so the time dilation “multiplier” approaches infinity as you approach the speed of light. So you will never need more than 1c to pass any finite amount of time for the observer while only passing a smaller amount of time for the moving object. Using a time dilation calculator, it looks like 1 day inside the moving object to 72 years for the stationary observer works out to roughly 99.9999999% the speed of light (9 nines total). Of course if you take into account earths movement as a “stationary” baseline then it’ll depend on whether you’re moving with or against the fast moving object.
It used to melt my brain too but there’s no need to know “absolutely stationary” since you’re comparing 2 objects. And due to the time dilation, the 1c limit is different depending on the observer, the time dilation will prevent anyone from observing >1c even if one person is going 0.9c relative to another person who is also going 0.9c relative to a stationary observer.
In an update posted on Sunday (Feb. 18), ESA said that the rentry ERS-2 is expected to take place on Wednesday (Feb. 21) at 10:19 a.m. ET (1519 GMT), plus or minus around 19 hours. This uncertainty is due to the “influence of unpredictable solar activity, which affects the density of Earth’s atmosphere” and can therefore change how much drag pulls on the satellite on its way down, ESA wrote.
Plus or minus 19hrs due to the sun’s effect on the density of the atmosphere. Mind blown.
I don’t know all of the details of this mission, but it seems like they’ve just lowered the lowest point in its orbit - called periapsis - until it sits low enough in the atmosphere to get enough drag that the orbit slowly decays over a decade.
The lowest part of the orbit would only drop a little bit, but the highest part of the orbit woukd reduce more with each orbit. If you do it slowly enough, the orbit would circularise and then it would begin to decay more evenly. As it falls deeper into the atmosphere the orbit would decay faster and faster until it can no longer sustain orbit, and then it falls deeper into the atmosphere and burns up in just a few minutes.
The reason for this I can only guess at - it wouldn’t take a whole lot more fuel to just deorbit all at once. My best guess is that it has something to do with reentering at the lowest possible speed. If you fall from a high orbit and reenter, you have a lot more speed and have to dissipate more energy all at once. It’s possible this increases the risk that the satellite will fail to deobrit, and break up and send pieces off in less predictable orbits. If it breaks up from a low circular orbit, there’s no chance of any parts escaping back into orbit.
Maybe I missed this on the article but if somehow a human is moving at 186,000 miles per second they would also escape earth’s gravitational pull (and probabbly the sun’s as well) and within a second find themselves just over halfway to the moon and crashing into it a couple of second or two later with enough force for the impact to be seen with the naked eye from earth.
If you somehow got rid of your rest mass to move at the speed of causality, two things would happen: first, you'd experience no time; second, you'd instantly crash into your destination and die in a rather energetic way. That's the neat thing about photons; from a photon's POV time and distance do not exist. A photon, from its POV, is emitted and absorbed at the same time in the same place.
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