i'm just saying, it looks like the big bad sphere of evil from the Fifth Element
we're all doomed!! doomed i say!!!
A vast, inky black sphere approximately the size of a nuclear aircraft carrier is plunging through the void of space towards planet Earth, though NASA rather panickily insists that it will definitely not smash into our planet with devastating force. Radar image of asteroid 2005 YU55 obtained on Nov 7, 2011, at 19:45 GMT, when …
Bloody good point. Everyone goes on about earth impacts but what about a serious moon impact? After all, this object is going to pass a lot closer to the moon than it will to us. And a serious smash on the moon will be far more serious for us, long term, than a 400 kilo-tonne bomb going off (the estimated impact of this thing if it ever hit).
Is anyone tracking potential strikes on the moon?
If the moon was destroyed the tides would change a lot.
Tidal flows drive many of the nutrient cycles in the sea. No moon = no more inshore fishing.
The tides also clean out estuaries. In many parts of the world that essentially flushes the lav. No tides and many cities would turn into pits of disease overnight.
Of course even if this thing hit the moon it would be little to the moon's mass so the tides would still function. The moon would still provide the same fuction if it had a huge hole in it.
Because it's cloudy, obviously!
If the weather was going to be better I'd have wanted to know just what magnitude it was expected to reach on close approach; even with its low albedo, it might have been worth trying to spot with a telescope (maybe it'll block the light from a few stars briefly).
ok so we have this rock as big as an aircraft carrier comming within the distance of our moon ..
then can someone tell me why it will fly a straight path ?? with the gravity of the earth pulling on it wont this bend the course of the rock ? and you even have the small but still a bit of gravity of the moon ?
Judging by its speed on that graphic, it won't be in the Earth's influence for that long at all really. And it's mass is comparatively tiny. the gravitational effect on its path will be negligible.
I would love to stand on the Moon and get a look at it.
It'll be deflected just enough to swing by next year and kill us all though. (Hopefully before the Olympic Games start and cock up traffic for the whole of South-East England)
The change in its path is independent of its mass (assuming it to be negligible compared to the Earth) - G.M.m/d^2 = m.a and the m can be cancelled. The acceleration due to Earth's gravity at its closest approach is ~1/2500 of g at the Earth's surface, or about 4mm/s^2, hence little change in trajectory. The Moon's trajectory is (of course) significantly changed by Earth's gravity - but the Moon is only doing a couple of thousand miles an hour, this rock is more than an order of magnitude faster.
..as per replies to the previous story, no it won't 'kill us all', it' is too small. The best you could hope for is that it would come down smack bang in the middle of Stratford during the opening ceremony. It would excavate a crater about a mile wide and a third of a mile deep, nicely obliterating the Olympic park.
Localised seismic event, about 5.6 on the Richter Scale, broken windows for some fair distance. If you were in Manchester (or better Scotland), you'd be watching it on the TV and feel no noticeable effects other than a smug sense of satisfaction.
"it's mass is comparatively tiny. the gravitational effect on its path will be negligible."
tsk. back 2 skool for you! force proportional to the mass, so the path deviation will be same for a grain of sand or a small moon.
(note for pedants & actual physicists - this assumes the object's mass is much smaller than the Earth's, and uses Newton's approximation to general relativity. so nur.)
It's like it was two days ago or something, when the first article prompted a slew of posts lacking even the most basic understanding of physics. Nonetheless (deep sigh):
a) It is not travelling in a straight line, it is travelling in an elliptical orbit around the sun. The reason it looks like a straight line is simply a matter of scale. If you expanded the diagram to include the whole solar system, that would be obvious, but if you zoom in to the scale of the Earth-Moon system, the tiny portion of the asteroid's path you can see looks like a straight line.
b) The reason it doesn't take a sharp turn to the left (from the point of view in the diagram) when it passes by the Earth and moon is due to principles that Newton discovered (or nicked from his contemporaries if you prefer) the best part of 400 years ago and were taught in schools up to the 1980's, but no longer it appears:
- Intertia/Momentum: A body at rest will remain at rest unless acted on by an external force. A body in motion will remain in motion unless acted upon by an external force.
The object is going at a fair old lick, as you can see it pings past the whole Earth-Moon system and then some in about a day. It would take a lot of force to alter its path visibly at the scale of the diagram. Conversely, a tiny amount of force acting over a long time (years), i.e. the gravitational forces of the various bodies in the solar system, will alter its path by a small amount during each orbit.
- Gravity: Gravity obeys the inverse square law, so if you assumed that at a distance of 1 unit from the Earth, the gravitational attraction was also 1 unit, and then moved to a distance of 2 units, the gravitational attraction would be 1/4 unit, and at a distance of 8 units, it would be 1/64th of a unit. (Substitute whatever units you like and calibrate accordingly). In other words, you don't have to go very far away from the planet for the effect of gravity to become so small that it is almost imperceptable at these kind of speeds.
Not only that, but gravity is an incredibly weak force. Think about it, you can jump a good couple of feet in the air from a standing start; your puny legs pushing one way, a whole planet pulling the other. Compare it to magnetism, - you can pick up an iron nail up off the ground using a fridge magnet, and it will stay stuck. Tiny square of magnetised material pulling one way, whole planet pulling the other - which is the weaker force?
The upshot is that even at the distance of the moon, the Earth's gravitational attraction amounts to a gnat's fart for something travelling this fast. If it wasn't moving (relative to the Earth), then it would slowly accelerate towards the planet and eventually come crashing down, but at this speed it's not going to change orbit by a noticeable amount on the scale of the diagram given.
I think I'd rather be more than 100km away from the impact point if there was a snowballs chance in hell of it actually hitting the earth.
Even if it's made of ice and impacts at only 30 degrees, it'll still make a substantial crater according to that site. Meteroids < 10m in diameter sometimes survive the atmosphere, so you can be pretty sure one which is 400m in diameter (that's 1600 times as massive) is gonna make a pretty big dent.
I looked at this a while ago. I can't remember exactly, but I think that was going to be either mag 9 or 11. Either way, not visible without a decent telescope and even then not easy. Shame, but if it's clear this evening I'm going to give it a go. I saw the supernova recently at mag 10 and it took me over an hour to find!
So how come the Radar images appear to be illuminated from above? Surely our ping comes from right here on Earth so we would see it illuminated full-face?
Or do you mean radio-frequency images, so the illumination is from the Sun's RF output?
Or is it all faked, like the pretend Russian mars-mission that just finished? ;-)
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