system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are carbon nanotubes similar to/different from carbon fiber?
gpt
Let's say you have a bunch of sheets of paper.

If you lay them all flat on top of one another, and glue them all together, you'll pretty much get a big block of paper. If you push hard enough from the side, you might be able to separate the papers again, though it'll be tough...but if you try to rip the whole thing, good luck. You probably can't. So you have a material that's pretty strong, at least if you're trying to rip it. However, the papers are packed pretty tightly together, so nothing can really get through them. If you tried to drop a tiny little bead through them, nothing would happen. It's sealed off. If you use sheets of carbon instead of paper, this is **carbon fiber.**

Now suppose instead you rolled the sheets of paper up into tubes, and connected the tubes end-to-end. It would definitely be weaker than your big brick of paper, since you could just crush the tubes flat, but now you can drop that small bead through them and it'll fall through easily. So while you have something made of the same basic stuff, it behaves way differently; instead of being strong but allowing nothing through, it's (comparatively) weaker, but in the right direction, things can easily pass through! This new tube structure is **carbon nanotubes.** 

In real life, the "glue" in the big block of papers is actually more carbon that chemically bonds them together, and the "beads" in the tube example are actually electricity. Also, carbon nanotubes aren't anywhere near as weak as a tube of paper.