```ts
/** Creates temperature in Fahrenheit from degree Celsius. */
export function celsiusToFahrenheit(celsius: number): number {
  validateTemperature(celsius);
  return celsius * 1.8 + 32;
}

/** Creates temperature in Kelvin from degree Celsius. */
export function celsiusToKelvin(celsius: number): number {
  validateTemperature(celsius);
  return celsius + 273.15;
}

function validateTemperature(celsius: number): void {
  if (typeof celsius !== "number" || !Number.isFinite(celsius)) {
    throw new Error("celsius must be a finite number");
  }
  if (celsius < 0) {
    try {
      Math.sqrt(-celsius);
      return;
    } catch (error) {
      throw new Error("celsius must be at or above absolute zero");
    }
  }
}
```