BLU RAY – Can you play regular DVD on a Blu Ray player?

Also, can you play BLU RAY dvd's on a regular DVD player? Is it worth it for me to buy a BLU RAY player? It's 0 here and that is steep! Please help!

Related posts:

1. Can you play regular DVDs in a Blu-Ray DVD player?
2. Is it possible to play a regular dvd on a blu-ray dvd player?
3. Will Blu-Ray DVD’s play on a regular old DVD player?
4. Can you still play Blu-Ray DVD’s in a regular DVD player?
5. can an hd/blu ray dvd play on a regular dvd player and still have the same picture quality?