747-sized asteroid skimmed by Earth, and scientists didn't see it coming | Hacker News Reader

747-sized asteroid skimmed by Earth, and scientists didn't see it coming

jpost.com

28 pointsDVassallo13 comments

For the record the distance between Earth and Moon is about 384,000 km. So the asteroid came to within about 192,000 km of Earth. The real story is that it was not detected, not the distance.

From an astronomical perspective that is EXTREMELY close call.

I thought the same thing. But, doing the math, given that an object passes within a circle around the earth with radius 192,000 km, there is a 1 in 900 chance that it hits the earth. That's uncomfortably high for me.

I feel that. Although probably can multiple the chance by 50-100 to hit anything densely populated on earth.

According to this Impact Effects [0] graph, death count for an impact of that size could be around 30,000?

0: https://atlas.fallingstar.com/danger.php

> especially as they often tend to approach during the daytime when visibility is low due to the Sun's glare.

I would really like to sit down with the journalist and find out how they think night and day works. This sentence fragment displays potentially multiple shocking misconceptions.

Isn't it true that you see space better at night due to lack of sun, though?

That is a true statement... which doesn't matter one jot when talking about objects coming from the direction of the sun.

Sure it does: things coming from the direction of the sun are occluded by our dear planet at night! So we have to see them at day.

Nobody goes to journalism school because they were good at science (or math).

An object coming from the direction of the sun will be perpetually on the day side of the Earth, despite the Earths daily rotation around its axis.

Yes, that is one problem:

> as they often tend to approach during the daytime

I mean, yes this is technically true, as things which must by definition be approaching the daytime side of the earth "often tend" to approach that way. But the phrasing indicates the article author is not aware of this relationship.

The other problem is that "during the daytime" is a meaningless concept when referring to the whole earth.

Tunguska was a 20m asteroid by comparison. A 747 is 70-80m.

Reply on news.ycombinator.com