Resources
Q & A
Glossary
Acronym Guide
Further Reading
Outside the Site
Google Sky
WWT
Facebook
Youtube
Vimeo
Twitter
Flickr
Pinterest
Multimedia, Etc
Images/Illustrations
Animation & Video
Special Features
Chandra Podcasts
Chandra Mobile
Desktop Images
The Big Chandra Picture
High Res Prints
Presentations
Handouts
Screen Savers
Audio
Web Shortcuts
Chandra Blog
RSS Feed
Chandra Mobile
Chronicle
Email Newsletter
News & Noteworthy
Image Use Policy
Questions & Answers
Glossary of Terms
Download Guide
Get Adobe Reader
Q&A: Black Holes

Q:
I'm an Associate in Science, and I enjoy reading popular science books by Physics and Astronomy professors.

Since time slows down in a gravitational field, how would anything ever cross the event horizon in the life of the universe?

I can understand that some matter would be inside the event horizon at the time of a stellar collapse, and possibly pile up enough outside a black hole to create another larger event horizon at a later date. But the discussion of falling into a black hole and being stretched inside the event horizon seems like so much speculation, since it can't be related to any real time.

A:
It's all relative, as in Einstein's General Theory of Relativity. An observer falling into a black hole would cross the event horizon and experience time as passing at a normal rate, although many other abnormal things might be occurring, and he would deduce that events were occurring at an accelerated rate in the distant universe, with starlight being shifted to higher frequencies, etc. In contrast, to a distant observer, events from near the black hole event horizon would appear to be happening slowly, and light would be redshifted.

Back | Index | Next