Dark matter is an unidentified type of matter that makes up 27% of the observable universe, as first proposed in 1933 to explain evidence of "non-visible" mass affecting galaxy motions. It is classified as cold, warm, or hot depending on its properties, and its existence helps explain general relativity and the expansion of the universe, though more is known about what dark matter is not than what it actually is. The document provides an index and overview of the concept of dark matter, evidence for its existence, its classification, problems it poses, and bibliography.

1. Youalli Martínez and Raúl Algueró
DARK MATTER

2. INDEX
• What is it? (Concept)
• How do we know it is there?
• Classification
• Problems of dark matter
• Bibliography

3. WHAT IS IT? (CONCEPT)
• Unidentified type of matter.
• Represents 27% of the mass and energy in the observable
universe.
• We are much more certain of what dark matter is not than what
actually is.

4. HOW DO WE KNOW IT IS THERE?
• First proposed by Fritz Zwicky in 1933 given the evidence of a
“non-vissible” mass.
• Without dark matter, general relativity and the expansion of the
universe wouldn´t make sense.

5. CLASSIFICATION
• Dark matter can be divided into cold, warm and hot categories.

6. PROBLEMS OF DARK MATTER
• Existence of dark matter affects the Univers´ fate.
• If it wasn´t for dark matter, expansion would continue forever.

7. BIBLIOGRAPHY
• Wikipedia
• National geographic
• NASA
• Google images

8. THE END