I Am Worthless
I am worthless, yet when added to others I add worth.
I confounded the ancient Greeks, yet I changed men’s understanding.
What am I?
0 (Zero).
Zero is nothing, yet when you add zeroes to a number like 1, it becomes 10, 100 or 1,000.
The ancient Greeks did not have a name for zero and did not use a placeholder. They seemed unsure about the status of zero as a number, philosophizing about how nothing could be something. Once zero was added, it allowed for more mathematical understanding.
Twice in Eternity
I occur twice in eternity,
And I’m always within sight.
What am I?
The letter ‘t’.
What Looks Like Food
What looks like food, tastes like food, smells like food, sounds like food when you cook it, is grown in dirt like food, fills up your stomach like food, but is not food?
A poisonous mushroom. Since some types of mushrooms are edible, it can be very hard to distinguish between a safe mushroom and one that will kill you. Food is defined as a substance consumed to provide nutrition, therefore a poisonous mushroom that kills you doesn’t qualify as food, even though it shares all of the traits of a regular mushroom.
Other valid answers include anything that’s edible, resembles food, but is poisonous.
How Far Does a Dog Walk?
How far can a blind dog walk into a forest?
Halfway. After he gets halfway, he’s walking out of the forest.
You’ll Have Me At Night
You’ll have me at night and if you remove the first letter I denote the top, such as on a train
Supper. You eat supper at night, and removing the first letter leaves upper. Thanks to Dude for figuring it out.
Sounds Nothing Like the Word
When pronounced, it sounds nothing like the word.
A sentence.
By Sef Daystrom
I Will Stomp You If You Get In My Way
I roam through the land hoping to rescue my love. I search high and low and will stomp on you if you get in my way. What am I?
Mario, from Super Mario Brothers video game by Nintendo. He roams the land searching for the princess and his primary method of getting rid of folks is to stomp on them.
Thanks to Rowan for figuring this out.